Physical activity (PA) and weight management have become important cancer prevention strategies. Research indicates that sedentary living and obesity are modifiable risks for many cancers. Thus, innovative strategies that facilitate better understanding of PA behavior to improve cancer control are imperative given the low levels of PA among Americans. A novel approach to PA that yields potent effects on health is high-intensity interval training (HIT), which involves segments of vigorous exercise interspersed with light activity or rest. These sessions are marked by short sprints conducted at near maximal effort for durations up to 60 seconds. HIT, therefore, represents a form of PA that is the polar opposite of low-intensity lifestyle PA. Importantly, several adaptive responses to HIT may be linked with reduced cancer risk including reductions in fasting insulin, abdominal obesity, and inflammation. The short-duration and low-volume characteristics of HIT make it a potentially desirable alternative to long-duration continuous exercise for improving PA levels in the general population, as HIT reduces the often-cited time barrier to PA participation. Research suggests that continuous high intensity PA reduces pleasure, which is likely to reduce long-term behavioral maintenance. However, the tolerability and pleasure associated with brief exposures to high-intensity interval work have not been evaluated. The primary aim of the study is to evaluate the affective and enjoyment responses to acute bouts of HIT and the secondary aim is to test the relationship between affective and enjoyment responses. The general hypothesis of the proposed short duration vigorous PA and may be preferable to continuous moderate PA because of the reduced time commitment. One hundred sedentary, overweight adults will complete a maximal exercise test and four subsequent exercise trials: two continuous (moderate intensity for 30 minutes and vigorous intensity for 20 minutes) and two discontinuous (one-minute interval; vigorous with recovery for 30 minutes and near-maximal with recovery for 20 minutes). Affect and enjoyment will be measured before, during, and after each experimental trial. The project is expected to facilitate future research to determine whether this form of exercise can be maintained long-term within populations at-risk for cancer and other negative outcomes. Such findings would therefore provide information about whether this highly beneficial form of exercise should be encouraged through public health recommendations.